Electrodynamic loudspeaker with basket mounting to pole piece

ABSTRACT

An improved construction for an electrical loudspeaker includes a housing enclosing a diaphragm and a magnetic motor structure secured to the housing. An aperture in the housing has a flange extending into a coaxial opening in the motor structure and crimped thereto, joining the housing to the motor structure and creating an air gap which has no machined surfaces or edges. An electro-magnetic voice coil secured to the diaphragm extends through the aperture in the housing and into the air gap, through which passes the magnetic field of the motor structure. Because the air gap has no machined surfaces or edges, it is free of chips and other foreign materials which are the major cause of speaker malfunction and failure. Furthermore, this method of construction is efficient and accurate and may be easily accomplished by automated methods.

United States Patent 11 1 Cohen et al.

[ Dec. 30, 1975 1 ELECTRODYNAMIC LOUDSPEAKER WITII BASKET MOUNTING TO POLE PIECE [76] Inventors: Hyman Cohen, 3898 Grosvenor Road, South Euclid, Ohio 44118; Paul Vago, 3396 Kildare Road, Cleveland Hts, Ohio 44118; Davorin Skender, 790 Babbitt Road, Euclid, Ohio 44123 22 Filed: May 14, 1974 21 Appl. No.: 469,879

11/1959 Germany 179/117 8/1958 Germany 179/115.5 VC

[57] ABSTRACT An improved construction for an electrical loudspeaker includes a housing enclosing a diaphragm and a magnetic motor structure secured to the housing. An aperture in the housing has a flange extending into a coaxial opening in the motor structure and crimped thereto, joining the housing to the motor structure and creating an air gap which has no machined surfaces or edges. An electro-magnetic voice coil secured to the diaphragm extends through the aperture in the housing and into the air gap, through which passes the magnetic field of the motor structure. Because the air gap has no machined surfaces or edges, it is free of chips and other foreign materials which are the major cause of speaker malfunction and failure. Furthermore, this method of construction is efficient and accurate and may be easily accomplished by automated methods.

2 Claims, 2 Drawing Figures [52] US. Cl 179/115.5 R [51] Int. Cl? H04R 9/02 [58] Field of Search 179/l15.5 R, 115.5 PC, 179/115.5 VC; 29/594 [56] References Cited UNITED STATES PATENTS 2,175,994 10/1939 Quam 179/117 2,532,414 12/1950 Levy 179/115.5 R

FOREIGN PATENTS OR APPLICATIONS 695,266 9/1965 Italy 179/1 15.5 PC 1,523,439 3/1968 France 179/ll5.5 R

U.S. Patent Dec. 30, 1975 3,930,129

FlG 1 ELECTRODYNAMIC LOUDSPEAKER WITH BASKET MOUNTING TO POLE PIECE BACKGROUND OF THE INVENTION housing by welding, spot welding, staking, drilled and,

tapped holes or other methods which may create more metal dust and particles. Because the particles cannot be completely removed, the subsequent magnetization of the motor structure draws the remaining particles into the air gap. The particles interfere with the clearance between the moving coil and the sides of the air gap, rubbing and causing severe distortion of reproduced sound, or blocking the moving coil altogether.

Another common failure of prior art loudspeakers is the misalignment of the magnet structure with the housing during assembly of the two parts. A slight misalignment during this assembly causes the air gap to be nonconcentric about the moving coil, causing rubbing and the resultant sound distortion.

Both the problems of chip and dust in the gap, and the misalignment of the magnetic structure have proved to be serious in the prior art, causing an unwarranted and costly high proportion of rejected loudspeakers during manufacture.

SUMMARY OF THE INVENTION The present invention is directed toward an improved construction of an electrical loudspeaker which overcomes the enumerated deficiencies of prior art devices. It comprises a speaker diaphragm which is enclosed in a housing, and an electromagnetic voice coil coaxially joined to the diaphragm and extending through an aperture in the housing. A permanent magnet motor structure with a plate adjoining the housing has an opening therein which coaxially registers with the aperture in the housing. A flange extruded from the edge of the aperture extends through the opening in the plate of the permanent magnet motor structure and is crimped into an annular groove about the opening of the plate, securing the housing and motor structure together and creating a smooth air gap in which the voice coil dwells.

THE DRAWING FIG. 1 is a partially cutaway side elevation of the present invention; and

FIG. 2 is an enlarged, exploded view of a portion of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the present invention includes a housing or basket 5, generally formed conically and symmetrically about axis AA. The housing includes a transverse annular portion 6, to which a conical diaphragm 7 is secured with adhesive. To the narrow end of the diaphragm a cylindrical coil form 8 is secured. Wound about the coil form is an electromagnetic voice coil 9, which provides the vibratory power for the diaphragm. A dust cap 11 seals the narrow end of the diaphragm and prevents any foreign material from entering and obstructing the voice coil. A flexible diaphragm or spider 12, secured about the narrow end of the diaphragm, similarly isolates the voice coil from contamination by airborn particles. The permanent magnet structure 13 includes a plate 14 of rectangular or circular configuration with a circular aperture 15 therethrough; the axis of the aperture coincident with axis A-A. The edges of aperture 15 are coined annular surfaces 17 and 20 as shown also in FIG. 2. A U-shaped bracket 18 is joined to the plate 14 by welding, adhesives or the like. Secured between the bracket 18 and the plate 14 is a cylindrical permanent magnet 19, to which a stepped cylindrical core piece 21 is joined. The magnet and core piece are axially coincident with the axis AA, and the smaller magnet is also polarized along this axis. Alternatively, a magnet of smaller radius may be employed, extending from the bracket 18 into the portion of the aperture occupied by the tip 21 shown.

With the core piece 21 extending into the aperture 15, a magnetic circuit to conduct the flux lines of the magnet is formed, comprising the magnet 19, the bracket 18, the plate 14, the air gap 22, the core piece 21 and again the magnet. Extending into the air gap is the voice coil 9, which is thus intersected by the flux lines of the magnet 19. An alternating current applied to the voice coil creates an alternating magnetic field which acts against the field of magnet 19, creating the varying force which causes the diaphragm 7 to vibrate.

The magnet structure 13 is secured to the housing 5 by means of a flange 23, which extends from the circular opening 24 in the narrow end of the housing 5, as shown in FIG. 2. A raised annular surface 25 is formed at the base of the flange. ln assembling the housing and magnet structure, the plate is joined to the housing with the flange extending into and through the aperture 15 and with the raised annular surface 25 fitting into the adjacent coined annular surface 17. The portion of the flange extending through the aperture is then crimped radially outward and onto the coined surface 20, securing the plate and its related magnet structure to the housing.

It should be noted that the members thus joined are centered with respect to each other. Because the outside diameter of the flange is just small enough to pass through the aperture 15 in the plate, the possibility of misaligning the housing and plate is eliminated. Furthermore, the process of joining the housing and magnet structure furnishes the air gap with an outer wall formed by the smooth surface of the flange. The machined edges of the aperture 15, which can contribute the minute metal shavings which rub against the moving voice coil and distort the reproduced sound are denied access to the air gap by the clean surface of the flange. Thus this method of speaker assembly also eliminates the major cause of loudspeaker malfunction that is encountered during manufacture.

Although the present invention has been described with respect to a particular form of housing and magnet structure, it should be appreciated that the present invention may be employed in other forms of loudspeakers. For example: the same speaker construction may be used with disc ceramic permanent magnets commonly known in the art, or with electromagnets.

We claim:

4 formed and an annular recess concentric about said aperture on one side of said plate,

said housing including an annular shoulder concentric about said circular opening and adapted to be received in said annular recess to center said housing with respect to said plate said flange receiving means including an annular groove concentric about said aperture on the other side of said plate, said flange means being crimped into said annular groove and retained thereby.

2. The electrical loudspeaker of claim 1, wherein said flange means comprises an annular flange about said circular opening and within said annular shoulder, and said electromagnetic means comprises a hollow, cylindrical electromagnetic coil concentrically and freely received within said annular flange. I 

1. An electrical loudspeaker comprising: a housing having a circular opening therein, diaphragm means secured within said housing for generating sound waves, magnetic means for creating a constant magnetic field, said magnetic means including an aperture therein, electromagnetic means secured to said diaphragm means, for vibrating said diaphragm means, flange means, formed integrally with said housing about said circular opening in said housing and extending through said aperture in said magnetic means, and flange receiving means within said magnetic means for retaining said flange means, said magnetic means including a plate in which said aperture is formed and an annular recess concentric about said aperture on one side of said plate, said housing including an annular shoulder concentric about said circular opening and adapted to be received in said annular recess to center said housing with respect to said plate said flange receiving means including an annular groove concentric about said aperture on the other side of said plate, said flange means being crimped into said annular groove and retained thereby.
 2. The electrical loudspeaker of claim 1, wherein said flange means comprises an annular flange about said circular opening and within said annular shoulder, and said electromagnetic means comprises a hollow, cylindrical electromagnetic coil concentrically and freely received within said annular flange. 